order the production of any document or other thing connected with the proceedings;

hear any additional evidence relevant to any alleged miscarriage of justice or order such evidence to be heard by a judge of the High Court or by such other person as it may appoint for that purpose;

take account of any circumstances relevant to the case which were not before the trial judge;

remit to any fit person to enquire and report in regard to any matter or circumstance affecting the appeal;

appoint a person with expert knowledge to act as assessor to the High Court in any case where it appears to the court that such expert knowledge is required for the proper determination of the case.